The carbon-copy (Cc) and blind-carbon-copy (Bcc) fields are hidden by default in AOL Mail. When composing a new message, click on their link to show them for a particular message: on the right, above the "To" recipient field in the email editor (when to use To, Cc, or Bcc).
But you can also make AOL Mail always show the Cc and Bcc fields by customizing your account: this spares you from having to manually show them every time!
From your inbox, click on "Options" (top right), and choose "Settings".
Select "Compose" on the left, and look at the first options.
Check the "Always show Cc field" and/or "Always show Bcc field" checkbox.
Scroll down and click on the "Save Settings" button.
Click "Back to Mail" and create a new message: all three recipients fields are now visible.
Tip: this setting affects your actual AOL email account, not just the current computer / web browser, and will be reflected from anywhere you login.